It is known that glass bodies can be micromachined using particular pulsed lasers. In a laser micromachining process, laser energy is directed into a material and a portion of the irradiated material is removed by ablation. Laser micromachining can be used, for example, to drill, cut, and scribe glass so as to form structures including, for example, channels, grooves, or holes in the glass material.
In some micromachining processes, the laser energy comprises one or more laser pulses. However, when more than a single laser pulse is used, residual heat can accumulate in the bulk of the remaining material as successive pulses are incident upon the material. If the laser pulse repetition rate is sufficiently high, the accumulated heating can become severe enough to cause undesirable effects, such as melting, or other changes to the surrounding regions of the glass material. These regions are known as Heat Affected Zones (HAZ), and they lead to imprecision in the micromachining process.
In some pulsed laser micromachining processes, a higher laser pulse repetition rate is necessary to make the micromachining process economically feasible. One micromachining approach utilizes formation of microcracks created by the high repetition lasers, followed by the etching of the microcracked areas. However, the microcracks may propagate into the surrounding area, which would lead to imprecision in the micromachining process. Another approach is to use a high repetition femtosecond laser with water or other liquid in contact with the glass, to clean out the removed glass as damaged regions are created.
Yet another approach utilizes lithographical etching of the glass. In this approach the photoresist material is deposited on top of the treated material. The photoresist is exposed with UV radiation and cured. Uncured photoresist can be removed, and whole part is exposed to acid. Only material without photoresist on the top will be etched. After etching remaining photoresist can be removed. There are different modifications of this approach, but all of them use photoresist and UV exposure to create desired pattern. The laser is used to expose and/or cure the photo resist material, not to change the glass.
Accordingly, apparatus and methods are needed that enable a more efficient and simple, or more exact way of laser micromachining.